ASP.NET WEB API的服务托管(Self-HOST)

如果我们想对外发布RESTful API，可以基于ASP.NET来构建Restful APIs，但需要部署IIS吗？答案是不必。你可以把它托管到一个Windows Service。具体如何把WEB API自托管到Windows Service可以参考这一文章：Self-Host a Web API (HttpSelfHostServer) (C#). 基本上照着一步步做就行了。例子里是基于Windows Console Application，同样可以Self-Host到Windows Service.

问题在于如何把Controllers从Windows Service分离？可以使用autoFac，本文具体从这展开。

使用autoFac分离Controllers

autoFac是一个.NET IoC容器框架，这里我们用来分离Controllers，也就是说，我们把MVC的控制器Controllers放到独立的一个工程（Project），然后在Windows Service里面自托管（Self-Host）RESTful APIs。部署的时候只要部署windows service即可，不需要IIS，外部一样可以调用我们的RESTful APIs. 需要做的就是： 1. 引用autoFac 2. 注册Controllers 3. 设置DependencyResolver。好，我们新建一个project，类型是类库dll。添加引用：System.Web.Http；添加一个Controller：

using System;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using Newtonsoft.Json;

namespace myCompany
{
    public class GroupController : ApiController, IGroupController
    {
        public HttpResponseMessage Update(HttpRequestMessage request)
        {
            Model model = null;
            var body = "";
            var valid = true;
            var result = new response { success = true, message = "" };
            HttpResponseMessage response;

            try
            {
                body = request.Content.ReadAsStringAsync().Result;
                /*
                 * According to the content type (text / json / xml), deserialize the request body
                 */
                model = Deserialize(body,
                    ModelUtility.GetMediaType(request.Content.Headers.ContentType.ToString()));

                if (model == null)
                    valid = false;
            }
            catch (Exception e)
            {
                valid = false;
            }

            if (!valid)
            {
                response = BuildFailureResponse(string.Format(
                    "Failure during parsing the request [{0}]", body));
            }
            else
            {
                 response = Request.CreateResponse(HttpStatusCode.OK, result);
            }
            
            return response;
        }

        private static Model Deserialize(string data, MediaTypes type)
        {
            switch (type)
            {
                case MediaTypes.HTML:
                    break;
                case MediaTypes.JSON:
                    return JsonConvert.DeserializeObject(data);
                case MediaTypes.TEXT:
                    return new Model
                    {
                        name = ModelUtility.ParseText(data, "name"),
                        status = ModelUtility.ParseText(data, "status")
                    };
                case MediaTypes.XML:
                    return Utility.XmlSerilizer.Deserialize(data);
                case MediaTypes.UNKNOWN:
                    break;
                default:
                    break;
            }
            return null;
        }

        private HttpResponseMessage BuildFailureResponse(string message)
        {
            var result = new response { success = false, message = message };
            return Request.CreateResponse(HttpStatusCode.BadRequest, result);
        }

    }
    
}

上面那个控制器可以处理RESTful API涉及group的请求。具体下面再谈。

回到我们已经创建Self-Host的Windows Service项目，里面添加引用Autofac.dll和Autofac.Integration.WebApi.dll。此外，可能还需要一些引用，我这里的列表如下：

然后在Windows Service项目里面添加一个类，内容如下：

using System.Reflection;
using System.Web.Http;
using Autofac;
using Autofac.Integration.WebApi;

namespace myCompany
{
    public class AutofacWebAPI
    {
        public static void Initialize(HttpConfiguration config)
        {
            config.DependencyResolver = new AutofacWebApiDependencyResolver(
                RegisterServices(new ContainerBuilder())
            );
        }

        private static IContainer RegisterServices(ContainerBuilder builder)
        {
            builder.RegisterAssemblyTypes(Assembly.GetExecutingAssembly()).PropertiesAutowired();

            builder.RegisterType().As();

            return builder.Build();
        }
    }
}

主要就是用来aufoFac初始化和注册类型。然后在Windows service里面调用：

 public partial class Service : ServiceBase
 {
        private HttpSelfHostServer _server;
        private readonly HttpSelfHostConfiguration _config;
		
        public Service()
        {
            InitializeComponent();
            
            _config = new HttpSelfHostConfiguration(_serviceAddress);
            _config.Routes.MapHttpRoute("DefaultApi",
                "notifications/{controller}/{id}",
                new { id = RouteParameter.Optional });
        }
		
        protected override void OnStart(string[] args)
        {
	 /* Start self-host Web API */
                AutofacWebAPI.Initialize(GlobalConfiguration.Configuration);
                _server = new HttpSelfHostServer(_config);
                _server.OpenAsync();
       }
 }

就这么简单。此外，你还可以用其他的DependencyResolver方式，具体参考autoFac官方文档：https://code.google.com/p/autofac/wiki/WebApiIntegration

最后如何测试呢？

HTTP POST http://localhost:8080/notifications/group/update

post body (text/plain): name=abc&status=CANCELLED
post body (application/json): "{\"name\":\"abc\",\"status\":\"CANCELLED\"}";
post body (application/xml):
      @"
         abc
         CANCELLED
      ";

看不懂的，可看代码。支持text/json/xml多种参数格式。RESTful API测试可以用Chrome插件：Postman REST Client。